Polymerization of cyclic esters



United States Patent 3,021,313 POLYMERIZATION OF CYCLIC ESTERS Eugene F. Cox andFritz Hostettler, Charleston, W. Va., assignors to Union Carbide Corporation, a corporation of New York No Drawing. Filed Dec. 3, 1959, Ser. No. 856,909 14 Claims. (Cl. 26078.3)

This invention relates to a process for polymerizing cyclic esters and to the products resulting therefrom.

"The most generally fam liar works on thepolymerization of 'lactones are'the now classical investigations of H. Carothers. For instance, Carothers was able to polymerize delta-valerolactone to poly-delta-valer'olactone by heating at'8085 'C. for a period of about 13 days, or by contacting delta-vaerolactone with potassium carbonate catalyst 'ata temperature of 80 85 C. for a period of about days. The resulting polymers were soft waxes possessing average molecular weights of approximately 2000 which had relatively low thermalstabilities. The literature reports that attempts to polymerize gamma-butyrolactone have been unsuccessful, and the corresponding polyester is not known. In 1934, there was reported 2 the preparation of poly-epsilon-caprolactone by heating epsi'on-caprolactone at about 150 C. for a period of 12 hours, or by contacting epsilon-caprolactone with potassium carbonate at about 150 C. for a period 'of:5 hours. The resulting eps lon-caprolactone polymers had melting-points of about 53 55 C; and average molecular weights of about 4000. The polymers were hard, brittle Waxes which could not be cold-drawn into fibers. Bischoff and Walden described the transformation of gycolide under the influence of heat or a trace of zinc chloride into a polymeric solid melting'at 220 C. On being distilled in a vacuum it was reconverted to the monomer melting at 8687 C. The literature also reports the polymerization of lactide at elevated temperatures to a resinous mass. A similar effect is also obtained at relatively lower temperatures by employing potassium carbonate as the catalyst.

In a broad aspect the present invention is directed to the process for polymerizing monomeric cyclic esters in contact with an aluminum alkoxide catalyst to produce useful polyester products, both the cyclic. ester reagents and the alkoxide catalysts being described hereinafter in a more appropriate section. The average molecular Weights of the resulting polymers can range from about severalhundred to about several thousand. The homopolymers, copolymers, and'terpolymers prepared by the practice of the instant invention are highly useful products as will'become apparent ata later section herein. In addition, the polymerizationreaction can be conducted at lower temperatures and .at faster poymerization rates heretofore unattainable in lactone polymerization art.

Accordingly, one or more of the following objects will be achieved by the practiceof this invention.

It is an object of thisinvention to provide anovel process for homopolymerizing monomeric cyclic esters to produce useful homopolymers. It is another object of this invention to provide a novel process for polymerizing an admixture containing at least two different monomeric cyclic'esters to produce useful polymers. A further object of this invention is to prepare lactone polymers. .having a high degree of utility and application in the cosmetic, wax, polish, thickening, molding, coating, etc.,

1 Collected Papers of Wallace H. Carothers, edited by H. Mark and G. S. Whitby, volume I, Interscience Publishers, Inc.. New York" (1940). V

' =F. J. van Natt a, J. W. Hill and W. H. Carothers, If our. Amer, Chem. $00., 06. 455 (1934).

3 Ben, 36,1200 (1903).

"ice

' fi'e'lds. Otherobjects-will become apparent to thoseskilled in 'theLart in the light of the instant specification.

In one-embodiment the monomeric cyclic-estersemployed in the polymerization process of this inventioncan be characterized by the following'formula:

1 (R-o-R) '(no-rn (Ah wherein each R, individually,.can be hydrogen, alkyl, .aryl, .alkaryl, aralkyl, cycloalkyl, halo, haloalkyl, alkoxyalkyl, alkoxy, aryloxy, and the like; whereinA can .be an oxy (-.O--) group, .a thio (.S-) group, a divalent saturated aliphaticv hydrocarbon group, and the like; wherein at is an integer from 1 to 15 inclusive; wherein y is an integer from 1 to 15 inclusive; wherein zis an (integer havinga value of zero or one; .withtheprovisos that (:a) the sum of x+y+z cannot equal 3, (b) the. total number of atoms forming the cyclic ester ring does not exceed 18, preferably does not exceed 9, (c) the total :numberof organic substituents (suchas those described for the ;R variables) attached to the carbonatoms contained in the cyclic ester ring does not exceed 4, preferably does not exceed 3, (d) from 2 to 4 continuously linked carbon atoms contained in the cyclic ester ring can represent a portion of a saturated cycloaliphatic hydrocarbon nucleus which contains from 4 to 10 ring carbon atoms, and (e) the four R variables attached to any two adjacent carbon atoms contained in the cyclic ester ring can represent a portion of a fused aromatic hydrocarbon nucleus.

With reference to Formula I supra, illustrative R radicals include, among others, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, t-butyl, amyl, the hexyls, the heptyls, the octyls, dodecyl, octadecyl, phenyl, benzyl, tolyl, xylyl, ethylphenyl, butylphenyl, phenethyl, phenylpropyl, phenylbutyl, cyclopentyl, 2-propylcyclohexyl, cyclohexyl, Z-methylcyclohexyl, cycloheptyl, chloromethyl, chloroethyl, bromopropyl, bromobutyl, chloro, fluoro, bromo, iodo, methoxymethyl, ethoxyethyl, propoxymethyl, butoxypropyl, methoxy, ethoxy, n-propoxy, n-butoxy, isopentoxy, n-hexoxy, Z-ethylhexoxy, 3-methyloctoxy, decoxy, dodecoxy, octadecoxy, phenoxy, ethylphenoxy, propylphenoxy, dimethylphenoxy, phenylpropoxy, and the like. It is preferred that each R, individually, be hydrogen, alkyl, and/ or alkoxy, and preferably still, that each R, individually, be hydrogen, lower alkyl, e.g., methyl, ethyl, n-propyl, isobutyl, and/or lower alkoxy, e.g. methoxy, ethoxy, propoxy, n-butoxy, and the like. It is further preferred that the total number of carbon atoms in the substituents attached to the cyclic ester ring does not exceed twelve. Cycloalkyl and lower alkyl-substituted cycloalkyl radicals which have from 5' to 7--carbon atoms in the cycloaliphatic nucleus .alsoare preferred.

.lnthediscussion'of the generic class of-monomeric cyclic esters (Formula I):contemplated in.the process of the inventionpfive provisosenumerated from (a) through (e) have been set forth. Proviso ,(a)-1states':that the sum of x+y+z cannot be a number equal to three. 'Ihis proviso excludes cyclic ester compounds which contain five atoms in the ring such as, for example,

a gammaebutyrolactone Prior art attempts. to polymerize gamma-butyrolactone "W. H. Caro'thers, G. L. Dorough, .and- F. .J. vanuNat a, Jour.;A.=mer. Chem.:Soe.,;54, 16111932). l t

five atoms in the lactone ring is much greater than the corresponding polymers, and that the free energy of interconversion is exceedingly low. Proviso (6) states that the total number of organic substituents attached to the carbon atoms contained in the cyclic ester ring should not exceed four, and preferably should not exceed three. It has been observed that when the total number of organic substituents on the cyclic ester ring approached "four or more, then the polymerizability of the cyclic ester monomer in the process of the invention diminished drastically, Proviso (d) states that from 2 to 4 continuously linked carbon atoms contained in the cyclic ester ring can represent a portion of a saturated cycloaliphatic hydrocarbon nucleus which contains from 4 to ring carbon atoms such as, for example, a saturated cycloaliphatic hydrocarbonnucleus derived from cycloalkane,

'falkyl-substituted cycloalkane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, methylcyclopentane, methylcyclohexane, and the like. Thus, for example, the following illustrative cyclic esters would be included in this proviso:

2-oxablcyclo 3.2.2 ]nonan-3-one Proviso (2) states that the four R variables attached to any two adjacent carbon atoms contained in the cyclic ester ring can represent a portion of a fused aromatic hydrocarbon nucleus, that is, an aromatic nucleus derived from benzene, alkylbenzene, methylbenzene, propylbengene, naphthalene, and the like. To illustrate this proviso, the following compound is depicted structurally.

2,3,4,5-tetrahydro-2-keto-benzoxepln In the structurally depicted compound immediately above, the fourR variables which were attached to the carbon atoms designated by numerals 6and 11 now represent a portion'of the fu's'edbenzene ring, namely the-carbon atoms designated by the numerals 7, 8, 9, and 10. The following compound further illustrates Pl'OVlSO (e).

2-(2'-hydroxymethy1phenyl)benzene carboxylic acid lactone Representative monomeric cyclic esters which can be employed as starting materials in the method of the invention include, for example, beta-propiolactone, deltavalerolactone, epsilon-caprolactone, 7-hydroxyheptanoic acid lactone, 8-hydroxyoctanoic acid lactone, 12-hydroxydodecanoic acid lactone, 13-hydroxytridecanoic acid lactone, 14-hydroxytetradecanoic acid lactone, l5-hydroxypentadecanoic acidlactone, lfi-hydroxyhexadecanoic acid lactone, l7-hydroxyheptadecanoic acid lactone; the alpha, alpha-dialkyl-beta-propiolactones, e.g., alpha, alpha-dimethyl beta-propiolactone, alpha, alpha-diethyl-betapropiolactone, alpha, alpha-dipropyl-beta-propiolactone, and the like; the monoalkyl-deltavalerolactones, e.g., the monomethyl-, monoethyl-, monoisopropyl-, monobutyl-,

monohexyL, monodecyl-, and monododecyl-delta-valerolactones, and the like; the dialkyl-delta-valerolactones in which the two alkyl groups are substituted on the same or different carbon atoms in the cyclic ester ring, e.g., the dimethyl-, diethyl-, diisopropyl-, dipentyl-, and din-octyl-delta-valerolactones, and the like; the monoalkyl-, dialkyl-, or trialkyl-epsilon-caprolactones, e.g., the monomethyl-, monoethyl-, monoisopropyl-, monohexyl-, mono= n-octyl-, dimethyl-, diethyl-, di-n-propyl-, diisobutyl-, di-nhexyl-, trimethyl-, triethyl-, and tri-n-propyl-epsilon-caprolactones, and the like; the monoalkoxyand dialkoxydelta-valerolactones and epsilon-caprolactones, e.g., monomethoxy-, monoethoxy-, monoisopropoxy-, dimethoxy, diethoxy-, and dibutoxy-delta-valerolactones and epsilon-caprolactones, and the like. Further illustrative cyclic esters include 3-ethyl-2-keto-1,4-dioxane, gamma- (1-isopropyl-4-methylcyclohexyl)-epsilon caprolactone, 3-brom0 2,3,4,5 tetrahydrobenzoxepin-Z-one, 2-(2-hydroxyphenyDbenzene carboxylic acid lactone, IO-hydroxyundecanoic acid lactone, 2,5,6,7-tetrahydrobenzoxepin-2- one, 9-oxabicyclo[5.2.2]undecan-S-one, 4-oxa-14-hydrox one, 9-oxabicyclo[5.2.2]undecan-8-one, 4-oxa-l4-hydroxytetradecanoic acid lactone, alpha, alpha-bis(chloromethyl)-propiolactone, 1,4-dioxane-2-one, 3-n-propyl-2 keto-l,4-dioxane, 3-(2-ethylhexyl) --2-keto 1,4 dioxane, and the like. Illustrative subclasses of cyclic esters which are eminently suitable in the process of the instant in vention include unsubstituted lactones and the oxalactones which contain from 6 to 8 atoms in the lactone ring, preferably delta-valerolactone, epsilon-caprolactone, the keto-dioxanes, and the like; the monoand polyalkylsubstituted lactones and oxalactones which contain from 6 to 8 atoms in the lactone ring, preferably the mono and poly-lower alkyl-delta-valerolactones, epsilon-caprolactones, and their corresponding oxalactones wherein the alkyl substituent(s) contains from 1 to 4 carbon atoms, and the like; and the monoand polyalkoxy-substituted lactones and oxalactones which contain from 6 to 8 atoms in the lactone ring, preferably the monoand poly-lower alkoxy-delta-valerolactones, epsilon-caprolactones, and their corresponding oxalactones wherein the alkoxy substituent(s) contains from 1 to 4 carbon atoms.

The unsubstituted and substituteddelta-valerolactones,

epsilon-caprolactones, zeta-enantholactones, and higher .monoand polyalkyl-substituted .epsilon-caprolactones, .monoand polyalkoxy-epsilon-caprolactones, .aryl-substituted epsilon-caprolactones, monoand polyhaloalkylsubstituted epsilon-caprolactones, .monoand polyalkyl- .substituted zeta-enantholactones, and variousother lactones described previously can be prepared by reacting the corresponding cyclic ketone with an anhydrous solution comprising peracetic acid and acetone. It is desirable to add the peracetic acid solution to-anexcessof .ketone, e.g., to 1 molar ratio of ketoneto peracetic .acid, in a still kettle maintained under reflux. The pres- .sure can be adjusted so as to provide a kettle tempera- .ture of, for example, about 70C. Acetone, acetic acid .by-produchand minor amounts of ketone can be continuously removed throughout the addition period. Subsequently, the lactone product can be recovered from the .still kettle by conventional techniques such as by distillation.

Stoll and Rouv report the preparation of lactones which contain up to 22 carbon atoms in the lactone nucleus 'by a process which comprises contacting the corresponding terminal hydroxy saturated aliphatic monocarboxylic acid with benzene-sulfonic acid catalyst in .boiling benzene. These authors also report the preparation of other lactones such as14-alkyl-l4-hydroxytetradecanoic acid lactone, e.g., l4-hydroxypentadecanoic acid lactone, and'oxa-lS-hydroxypentadecanoic acid lactone, e.g., lZ-oxa-15-hydroxypentadecanoic acid lactone. Palomaa and Tonkola teach the preparation of 3-oxa-6 rhydroxyhexanoic acid lactone by heating the correspond- :ing terminal hydroxy saturated aliphatic monocarboxylic acid. The preparation of 2-keto-1,4-dioxane, -3-alkyl-2- keto-l,4-dioxane, polyalkoxy-substituted delta-valerolac- .tone, monoand polyalkyl-substituted delta-val'erolactone, alkoxyalkyl-substituted delta-valerolactone, etc., is recorded by Carothers et al. The preparation of dialkylsubstituted, dihalo-substituted lactone, e.g., gamma, delta- 'dibromo-gamma, delta-dimethyl-delta-valerolactone is reportedin the literature by Levina et al. German .Pat. No. 562,827 discloses the preparation of 2,3, 1,5- -tetrahydrobenzoxepin-Z-one whereas the literature re- .ports the position isomer, namely 2,5,6,7-tetrahydrobenzoxepin-Z-one. Cycloalkyl-substituted epsilon-caprolac- -tone, e.g., gamma(l-isopropyl-4-methylcyclohexyl)-epsi- :lon-caprolactone is disclosed by Belov and Kheifits. -McKay et al. 11 have recorded the preparation of halosubstituted, haloalkyl-substituted delta-valerolactone. The literature also reports the preparation of various other cyclic esters.

The metal alkoxides contemplated as catalysts in the process of the invention can be characterized by the following formula:

wherein OR represents an alkoxy radical'such as, for example, methoxy, ethoxy, isopropoxy, n-propoxy, nbutoxy, sec-butoxy, t-butoxy, pentoxy, hexoxy, isohexoxy, 2-ethylhexoxy, n-cctoxy, Z-methyloctoxy, decoxy, 'dodecoxy, hexadecoxy, octadecoxy, and the like. Preferably the alkoxy group in the catalyst contains up to carbon atoms, particularly 2 to 4 carbon atoms. Illustrative "aluminum alkoxides include, among others, aluminum methoxide, aluminum ethoxide, aluminum isopropoxide, aluminum n-propoxide, aluminum isobutoxide, aluminum t-butoxide, aluminum n-butoxide, aluminum hexoxide, aluminum Z-ethylhexoxide, aluminum octoxide, aluminum dodecoxide, aluminum octadecoxide, and the like.

The catalysts are employed in catalytically significant quantities. In general, a catalyst concentration in the He1v. Chim. Acta. 18, 1087 (1935). Ben. 66. 1629 (1933).

7 See footnote 1.

B Zhur ()hshchei Khirn, 24, 1439 (1904). '"Bera. 68B, 1170 (]935) J. Gen, Chem. USSR, 27, 1459 (19;)7).

' Amer; Chem. Soc., 77, 5601-6. (1955).

range .of from about.0.001, and lower, to about l0,*and higher, weight percent, based on the weight of total .monomericfeed, is. suitable. A catalyst concentration in .the ranged from. about 0.01 to about 3.0.weightpercentis preferred. A catalyst concentration in the range. offrom about 0.05 to about 1.0 weight percent is highly preferred. For optimum results, the particular catalystemployed, the nature of the monomeric reagent(s), the op- :erative conditions under which the polymerization reaction is conducted, and other factors will largely determine the desired catalyst concentration.

The polymerization reaction can be conducted over a wide temperature range. Depending upon various factors such as the nature of the monomeric reagent(s) employed, the particular catalyst employed, the concentration of the catalyst, and the like, the reaction'temperature can be as low as 20 C., and lower, and as high as 250 C., and higher. A suitable temperature range is from .about 0 to about 225 C. A reaction temperature in the rangeof from about 20 to about 200 C. is preferred.

The polymerization reaction preferably occurs in the liquid phase, and to this extent sufiicient pressure is employed to maintain an essentially liquid reaction mixture regardless whether or not an inert normally-liquid organic vehicle is employed. Preferably, the polymerization reaction is conducted under an inert atmosphere, e.g., nitrogen, butane, helium,'etc. The ultimate molecular weight of the resulting polymer will depend, to an extent, upon various factors such as the temperature, the choice and concentration of the catalyst, the use .and amount of an inert normally-liquid organic vehicle(s), and the like.

In general, the reaction time will vary depending on the operative temperature, the nature of the monomeric cyclic esters employed, the particular catalyst and the concentration employed, the use of an inert normally-liq- ,uid organic vehicle, and other .factors. The reaction time can vary from several seconds to several hours, or more, depending on the variables illustrated above.

' It is preferred to conduct the polymerization reaction in the essential absence of impurities which containactive hydrogen since the presence of such impurities .tendsto deactivate the catalyst and/or increase the induction period. The minimization or essential avoidance of impurities such as water, carbon dioxide, aldehydes, ketones, etc., is highly desirable. It is also preferred that the polymerization reaction be conducted under substantially anhydrous conditions.

When polymerizing an admixture containing at least two different cyclic esters, the proportionsof said cyclic esters can vary over the entire range. Broadly theconcentration of each monomeric cyclic ester is in the range of from about 3 to about 97 weight percent, based on the total weight of said cyclic esters. The preferred range is from about 15 to about weight percent. Admixtures containing epsilon-caprolactone and monoand/or polyaLkyl-substituted epsilon-caprolactone (including isomeric .mixtures thereof) are highly preferred as starting materials in the process of the invention. Admixtures containing different monoand/or polyalkyltsubstituted epsilon-caprolactones (including isomeric mixtures of the .same and/or differentmonoand/ or polyalkyl-substituted epsilon-caprolactones) also are highly preferred.

The polymers of this invention can be prepared via .the bulk polymerization, suspension polymerization, or the solution polymerization routes. The polymerization reaction can be carried out in the presence :of an inert normally-liquid organic vehicle such as, for example, aromatic hydrocarbons, e.g., benzene, toluene, xylene, ethyl- .benzene, and the like; various oxygenated organic compounds such as anisole, the dimethyl and diethyl ethers .of ethylene glycol, of propylene glycol,.of diethylene glycol, 'and the like; normally-liquid saturated hydrocarbons including the-open chain, cyclic, and .alkyl-substituted cyclicsaturated hydrocarbons such as hexane, heptane,

various normally-liquid petroleum hydrocarbon fractions, "cyclohexane, the alkylcyclohexane, decahydronaphthalene, and the like.. If desired, a mixture of mutually miscible inert normally-liquid organic vehicles can be employed.

The process of the invention can be executed in a batch, semi-continuous, or continuous fashion. The reaction vessel can be a glass vesseh'steel autoclave, elongated metallic tube, or other equipment and material employed in the polymer art. The order of addition of catalyst and monomeric reagent(s) does not appear to be critical. A suitable procedure is to add the catalyst to the reaction zone containing the monomeric reagent(s) and inert organic vehicle, if any. If desired, the catalyst can be in solution or suspension (in an inert normally-liquid organic vehicle). Incremental addition of catalyst to the reaction zone can be employed. If desired, the above procedure can be reversed, that is, the monomeric reagent(s) per se or as a solution or suspension in an inert organic vehicle can be added to the reaction zone containing the catalyst (or a catalyst solution or suspension). Also, the catalyst, reagent(s), and inert organic vehicle, if any, can be added to the reaction Zone simultaneously. The reaction zone (be it a closed vessel or an elongated tube) can be fitted with an external heat exchanger to thus control undue temperature fluctuations, or to prevent any possible run-away reaction temperatures due to the exothermic nature of the reaction. In a continuous operation employing as the reaction zone an elongated tube or conduit, the use of one or a plurality of separate heat exchangers can be conveniently used. In a batch operation, stirring means can be provided for agitating the reaction mixture, as desired.

Unreacted monomeric reagent oftentimes can be recovered from the reaction product by conventional techniques such as by heating said reaction product under reduced pressure. Removal of unreacted monomeric reagent(s) and/or inert organic vehicle can be accomplished by mechanical means such as treatment of the reaction product in a Marshall Mill and the like. The polymer product also can be recovered from the reaction product by washing said reaction product with an inert normally-liquid organic vehicle, e.g., heptane, and subsequently drying same under reduced pressure at slight- 1y, elevated temperatures. Another route involves dissolution in a first organic vehicle, followed by the addition of a second inert organic vehicle which is miscible with the first vehicle but which is a non-solvent for the polymer product, thus precipitating the polymer product. If desired, the reaction product can be dissolved in an inert organic vehicle such as acetone, and the like, followed by the addition of suflicient water to the resulting solution, said water being miscible with said inert organic vehicle but being a non-solvent for the water-insoluble polymer thereby precipitating the polymer product. Recovery of the 'precipitated polymer can be effected by filtration, decantation, etc., followed by drying same as indicated previously. If desired, the polymer product also 'can be freed of catalyst residue, if any, by extraction with dilute mineral acid such as hydrochloric acid or sulfuric acid.

The linear polyester products resulting from the process of the invention can be characterized by the following recurring structural unit:

L lla. filial L\t/x \t/. 1

about several thousand. The ultimate molecular weight and properties of the polyester products will depend, in "the main, upon the choice of the cyclic ester(s) and catalyst, the concentration of the catalyst, the operative conditions employed, e.g., temperature, etc., the purity of the monomeric reagent(s) and catalyst, the use and amount or an inert normally-liquid organic vehicle, and the like.

It is readily apparent thatthe linear homopolymers are essentially characterized by the same recurring unit which falls within the scope of Formula III supra. 'Ihe copolymers, terpolymers, etc., on the other hand, can contain as little as 1.0 weight percent, and lower, and upwards to 99 weight percent, and higher, of the same recurring unit. Desirable polymers are those in which the weight percent of the different recurring units is in the range of from about 3 to about 97. In the highly preferred copolymers the weight percent of the two different recurring units is in the range of from about 15 to about 85. l

The polymers obtained by the process of the invention are a useful class of polyester compounds. These polymers can range from viscous liquids to very tough solids. The polymers in the range of from very viscous liquids to "relatively low molecular weight, wax-like solids are useful in the preparation of cosmetics, polishes, and waxes, and as thickening agents for various lubricants. The polymers can be employed to size cellulosic material or they can be used as anti-static agents in the treatment of fibrous materials. They can also be employed as protective coatings and/or impregnants. The solid polymers are useful for the production of various shaped articles such as brush handles, buttons, lamp bases, toys, and the like.

In passing, it should be noted that one apparent advantage afforded by the practice of the invention is the preparation of copolymers, terpolymers, etc., whose physical characteristics can be tailor-made to fit desired fields of applications and uses. In other words, by adjusting the concentration of the monomeric charge to a particular polymerization system, copolymers, terpolymers, etc., which cover a wide spectrum of properties and characteristics can be prepared, e.g., soft, rubbery polymers to hard, solid polymers.

In the illustrative operative examples to follow, the polymeric product oftentimes is described as possessing a certain reduced viscosity value. By this term, i.e., re-

duced viscosity, is meant a value obtained by dividing the specific viscosity by the concentration of the polymer in the solution, the concentration being measured in grams of polymer per 100 milliliters of solvent at a given temperature. The specific viscosity is obtained by dividing the difference between the viscosity ofzthe solution and the viscosity of the solvent by the viscosity of the solvent. The reduced viscosity value is an indication of the molecular weight of the polymer. Unless otherwise indicated, the reduced viscosity value was determined at 30 C.

Also, in the illustrative operative examples below, the polymerization reaction was generally conducted under an inert atmosphere, e.g., nitrogen. The reaction vessel and contents, i.e., cyclic ester(s), catalyst, and inert organic vehicle, if any, were maintained, usually under agitation, in a constant temperature, e.g., 90 C., or the reaction vessel containing the cyclic ester(s) was maintained, usually under agitation, in a constant temperature and subsequently the catalyst was added thereto. Since the polymerization reaction, in general, was exothermic a rise in temperature was observed, e.g., to C. In several instances the period recorded was the time observed in which the rotation of the mechanical stirrer ceased due to the high viscosity of the contents in the reaction vessel. In most casesthe reaction vessel was left in the constant temperature bath for an additional period of time, e.g., about 20 minutes, or longer. .Unless otherwise indicated-the examinationondescription of the'polymeric product-was-conducted at room-temperature, i.e., about 23 C. In general, theconversion of monomer to polymer was quantitative.

EXAMPLE 1 A. To .a reaction vesselmaintained under a nitrogen atmosphere and which contained epsilon-caprolactone, there was chargedaluminum isopropoxide .in an amount so as to give an admixture containing 0.5 weightpercent aluminum isopropoxide, based on the weight of said epsilon-caprolactone. The reaction vessel then was placed in a constant temperature bath maintained at 90 C. Within 8 minutes the'mechanical' stirrer ceased due to the high viscosity of the contents in the reaction vessel. Thereafter, the reaction product was dissolved in acetone and reprecipitated .in water. There was .obtained a tough, white, crystalline solid homopolymer which possessed a reduced viscosity value of 0.86 (measured at 0.4 gram of polymer in 100 ml. of chlorform).

B. In an analogous manner as above, when beta,gamma-dimethoxy-delta valerolactone is substituted for epsilon-caprolactone and contacted withliO weight percer'it aluminum n-butoxide, there is obtained a solid polymer.

EXAMPLE 2 A. To a reaction vessel maintained under a nitrogen atmosphere and which contained epsilon-caprolactone, there was charged aluminum ethoxide in xanamount so as to give an admixture contain ng 0.5 weight percent aluminum ethoxide, based on the weight of said epsilon caprolactone. The reaction vessel'then Wasplaced-in-a constant temperature bath maintained at 90 C. for a period of 3 hours. The temperature then was raised to 150 C. for-a period of 16 hours. There was obtained a soft, waxy, solid homopolymer which possessed a reduced viscosity value of 0.33 (measured at 0.4 gram of I polymer in 100 ml. of chloroform).

B. In an analogous manner as above, when aluminum 2-ethylhexoxide is substituted for aluminum ethoxide in an amount so as to give an admixture which contains 1.0 weight percent of aluminum Z-ethylhexoxide, based .on the weight of epsilon-caprolactone, essentiallythe same resultsare obtained.

EXAMPLE3 A. To -a reaction vessel maintained under a nitrogen atmosphere and which contains epsilon caprolactone, there is charged aluminum isopropoxide in an amount so as to give an admixture containing 0.7 weight percent aluminum isopropoxide, based on the weight of said epsilon-caprolactone. The reaction vessel 'then is placed in a constant temperature bath maintained at 90 C. for a period of minutes. Thereafter, the polymeric prodnet is recovered. There -is-obtained "EfOllgh solid.

B. In an analogous manner as. above, when gamma (1-isopropyl-4-methylcyclohexyl -epsilon-caprolactone is substituted for epsilon-caprolactone and contacted with 0.7 weight percent aluminum -n-octoxide,-there-isob tained a viscous liquid product.

EXAMPLE 4 A. To a reaction vessel maintained under a nitrogen atmosphere .and .W'hlChLCOl'ltHlIld epsilon caprolactone, Qthereischarged aluminum tebutoxide in? an .amountiso "as to give anadmixturecontaining 0.6 'weighti'percent aluminum t-butoxide, based. on the :weight. of saidzepsiloncaprolactone. The reaction'vessed. then isplaced inaccu- .stant temperature'bath.maintainedat 90 .C.-for. a period .of 25 minutes. Thereafter, .thepolymeric .product is recovered from the reaction vessel. Thereiis: obtained :a tough, white homopolymer.

.113. In ananalogous manner as-iahove, whengamma- .methyl delta-isopropyleepsilonecaprolactone, .is substituted :for: epsilon capro'lactone and-contacted with 1.0 weight percent: aluminum isopropoxide, there is obtained -a very viscous liquid homopolymer.

*10 EXAMPLE-.5

A. To a reaction vessel maintained undera'nitrogen atmosphere and which contains anisomeric mixture of methyl-epsilon-caprolactone, therepis charged aluminum octadecoxide in an amount so as to given .an admixture containing 0.5 weight percent aluminum octadecoxide, based on the total weight of methyl-epsilon-caprolactone. The isomeric mixture contains, by weight,approximately 30 percent gamma-methyl-epsilon-caprolactone, about :30 percent epsilon-methyl-epsilon-caprolactone, and about 40 percent beta-methyland delta-methyl-epsilon-caprolactone. ,This isomeric lactone mixture is prepar,ed by reacting a mixture of 2-methyl-, 3-rnethyl-, and 4-methylcyclohexanone with peracetic'acid. The reaction vessel then is placed in a constant temperature bath maintained at 90 C. for a period of 3'hours. 'Thereafter, the polymeric product is recovered. There isobtainedawery viscous liquid product.

B. In an analogous manner as above, when 2-bromo- 2-(3'-bromopropyl)-5-hydroxypentanoic acid lactone is substituted for the isomeric mixture of methyl-epsiloncaprolactones and contacted with 1.0 weight percent aluminum isopropoxide, substantially "similar results are obtained.

4 EXAMPLE *6 A. To a reaction vessel maintained 'under a' nitrogen atmosphere and which contains an isomeric mixture composed of a major proportion by weight ofgamma-octylepsilon-caprolactone and a minor proportion by weight .of epsilon-octyl-epsilon-caprolactone, there is charged aluminum 2-ethylhexoxide in an amount so .as 'to-lgive an admixture containing 0.6 weight percent aluminum;2- -ethylhexoxide,.based on thetotal weight of octyl-epsiloncaprolactone. The reaction vessel then is .placed in a constant temperature bath maintained at 90 C. for a -period of 15 minutes. There is obtainedfla very viscous .liquid product.

B. In an analogous manner as above, when 23,4;5- tetrahydrobenzoxepin-Z-one is substituted for the isomeric mixture of octyl-epsilon-caprolactones and contacted with 1.0 weight percent aluminum dodecoxide, there is obtained a soft solid polymer.

EXAMPLE 7 A. To a reaction vessel maintained under a nitrogen atmosphere and which contains delta-valerolactone, there is charged aluminum isopropoxide in an amount so as to. ,give antadmixture containing- 0.5 weight percent-aluminum isopropoxide, based on the weight of said deltavalerolactone. The reaction vessel then is placed 'in a constant temperature bath maintained at 90 C. ..for.. a period of one hour. Thereafter, the polymeric product is recovered. There is obtained a solid homopolymer.

B. luau analogous manner-as above, when '3=ethyl-2- keto-1,4-dioxane is substituted for delta-valerolactone and contacted with 1.0 weight percent aluminum isopropoxide, a very viscous.liquidproduct.is.obtained.

EXAMPLE 8 A. To a reaction vessel maintained under a nitrogen atmosphere and which contains beta-methyl-delta valerolactone (redistilled, 'boilingpoint 137 C. at 1.5 mm. of Hg; n of 114480) there 'is charged aluminum 'fisopropoxide in an amount so as to give an admixture containing- 1.0 weight percent aluminum "isopropoxide, based on the weight of said beta methyl=delta=valerolactone. The reaction vessel then is placed -in a' constant'temperature bath which is maintained at 90 C. for a period of about 35 minutes. Thereafter, thepolymeric product is recovered. There is obtained-a solid-product.

B. In .an analogous manneras above,'----when 3-'oxa-6- -:hyclroxy-hexanoic acid lactone is substituted for betamethyl delta valerolactone and cont-acted with '05- weight the presence of aluminum isopropoxide. The procedure 1'1 12 percent aluminum methoxide, essentially similar results 'weight percent aluminum octade'coxide, there is obtained are obtained. a very viscous liquid.

EXAMPLES 9-11 EXAMPLES 16 17 In Examples 9 through 11, various copolymers are prepared by polymerizing an admixture of two lactones in In Examples 16 and various copolymers are pared by contacting, at 90 C., a mixture of epsilon- 'caprolactone and delta-valerolactone with 0.5 weight peremployed is similar to that set forth immediately precedcent of alummum isopropoxide, based on the total weight ing the operative examples. The pertinent data and results are recorded in Table I below. of the lactone feed. The procedure employed is similar Table I Example Catalyst Temp, Time, Description of Number Lactone Charge 1 Concen- 0. Min. Copolyiner tration 2 9 70 epsilon-caprolactone/3O beta-methyl- 0. 6 90 9 Tough solid.

delta-valerolactone. 10 80 epsilou caprolactouelzu beta-methyl- 0.6 90 9 Do.

delta-valerolactone.

11 85 epsilon-caprolactone/l5 beta-methyl- 0.6 9O 18 White, waxy solid.

delta-valerolactone.

' 1 Parts by weight. 7 Weight percent calalyst, based on total weight of lactone charge.

EXAMPLE 12 to that set forth immediately perceding the operative A. To a reaction vessel maintained under a nitrogen z i g g s pertinent data and results are recorded m atmosphere and which contains zeta-enantholactone, a e

there is charged aluminum isopropoxide in an amount so Table 111 as to give an admixture containing 0.5 weight percent aluminum isopropoxide, based on the weight of said Ratio of zeta-enantholactone. The reaction vessel then is placed Epsilonin a constant temperature bath maintained at 90 C. Example Number g g f kg f k f Descgifptmn for a period of 20 minutes. Thereafter, the polymeric erolt ictone Copolymer ,productis recovered. There is obtained a white, solid homopolymer. 16 20:80 8 White solid. B. In an analogous manner as above, when IO-hydroxy- 17 80 20 4 T h s li undecanoic aicd lactone is substituted for zeta-enantholactone and contacted with 0.7 weight percent aluminum s parts by weight. t-butoxide, essentially similar results are obtained. EXAMPLE 18 EXAMPLES 13-14 A. To a reaction vessel maintained under a nitrogen In Examples 13 and 14 the procedure employed is atmosphere and which contains a mixture of 80 parts by similar to that set forth immediately preceding the operaweight of epsilon-caprolactone and 20 parts by weight of tive examples. The pertinent data and results are remixed dimethyl-epsilon-caprolactones, there is charged corded in Table H below. 7 aluminum isopropoxide in an amount so as to give an ad- Table 11 Example Catalyst Temp., Time, Description of Number Lactone Charge 1 Catalyst Concen- 0. Min. Polyester tration 13 30 zeta-enantho1actone/70 Ala-00 m); 0.50 90 15 Hard, white solid.

epsilon-caprolactone. 14 20 zeta-enantholaotone/SO Al(i-OCaH1); 0.50 90 13 Tough, white solid.

' epsilon-caprolactone.

1 Admixture of two lactones is expressed as parts by weight. Weight per cent catalyst, based on total weight of lactone charge. N orE.-Zeta-enanthol actone redistilled; B.P. 72 C. at 4mm. of Hg; n9 of 1.4689.

EXAMPLE 15 mixture containing 0.5 weight percent aluminum iso- A. To a reaction vessel maintained under a nitrogen g i B E the-Total welglht theE lame-n8 atmosphere and which contains 2-keto-1,4-dioxane, there mlxe y ep 51 o-mcapm actones 18 an 'is charged aluminum isopropoxide in an amount so as to mlxture betagamma-dlmethyland gammaflehadl methyl-epsilon-caprolactones. The reaction vessel then w admlxtmje contammg wFlght Percent is placed in a constant temperature bath maintained at mmum lsoprqpoxldfc based on the weght of said 90 C. for a period of 3 hours. There is obtained a soft 1,4-d1'oxane. The reaction vessel then is placed in a solid product constant temperature bath maintained at 90 C. for a In an analogous manner as above, when equal parts spenod f a one hour- 3 the Polymer: by weight of 12-oxa-l5-hydroxypentadecanoic acid lac- Pwdlmt 1S recovelfed- There 15 Obtalfled a Solid p y tone and 7-hydroxyheptanoic acid lactone are employed 1 Q B. In an analogo s m nn above, When g uas the monomeric feed and contacted with 1.0 weight ylsopropyl 4-methylcyclohexyl)-epsilon-caprolactone is percent aluminum n-octoxide, substantially similar. results substituted for 2 -keto-1-,4-dioxane and contacted with 1.0 are obtained.

eapana 1a "13 ZEXAMPLEI 19 A. To a reaction "vessel maintained under a'nitrogen atmosphere and which contains 'a rnixture of 50 parts by weight of epsilon-caprolactone and 5.0 parts by weight of mixed octyl 'epsilon-caprolactones; there is charged alumi- 'num isopropoxide in an "amount so as to give an admixture containing'0.5 weight percent; aluminum. isopropox- Tide, based on the total'weightof the lactonetfeed. 'The mixed .octyl-caprolactones comprise a major proportion by weight of gammaaoctyl and;a minorproportion -by weight of epsilon-octylrepsilon-caprolactones. The reaction vessel then is placed in'a'constant'temperature bath maintained at 90 .C. for ax'period of one hour. "Thereafter, the reactiontproduct is dissolved in1acetone and reprecipitated in water. There 'is obtained a" waxy .copolymer.

B. In an analogous manner as above, when equal parts by weight of 9-oxabicyclo[5.2.2]undecan-8-one and 1,4- dioxane-2-oneare employed as the monomericifeed and contacted with 1.0 weight percent aluminum tethoxide,

essentially similar results'are obtained.

EXAMPLE 20 To a reaction vessel maintained under a nitrogen atmosphere and which contains equal parts, by weight,"'of

phenylactic acid lactone, there is charged aluminum isopropoxide in an amount so as to'givean admixturecontaining 0.50 weight percent aluminum isopropoxide, based on the Weight of said ortho-(2-hydroxyethyl)-phenylacetic acid lactone. The reaction vessel then is placed in a. constant temperature bath maintained at 90 C. for a period of 10 minutes. There is obtained a solid polymer.

B. In an analogous manner as above, when cis-3-oxabicycl[5.4.0] undecan-4-one is substituted for ortho-(2-hydroxyethyD-phenylacetic acid lactone and contacted with 1.0 Weight percent aluminum t-butoxide, essentially similar results are obtained.

Although the invention has been illustrated by the preceding examples, the invention is not to be construed as limited to the materials employed in the above exemplary examples, but rather, the invention encompasses the generic area as hereinbefore disclosed. Various modifications and embodiments of this invention can be made without departing from the spirit and scope thereof.

What is claimed is:

1. A process which comprises polymerizing a cyclic ester characterized by the following formula:

wherein each R, individually, is selected from the group consisting of hydrogen, alkyl, aryl, alkaryl, aralkyl, cycloalkyl, halo, haloalkyl, alkoxyalkyl, alkoxy, aryloxy, a portion of an aromatic hydrocarbon nucleus which nucleus is fused to the cyclic ester ring, and a portion of a saturated cycloaliphatic hydrocarbon nucleus which nucleus contains from 4 to carbon atoms and which is fused to the cyclic ester ring; wherein A is selected from :thergroup consistingpf-ian :oxy group, athio group, and a divalent saturated aliphatic hydrocarbon group; where- ---in:x:isran integer in the :range :of from 1v to- 15 inclusive; .xwherein. yris an integerin the range of .from.1 to 15 in- .tclusive; and where inzzis an integer. selected from the "group'consistingof zero and one; with theprovisos that (althesum of x+y+z cannot equal three, (b) the total number. of atoms. forming :the -cyclic ester. ring does not :exceed .18, and .(c):the.total number of 'organicsub- :stituentsgattached-"to' .the :.car.bon.,atoms. contained in the cyclic ester ring does not exceed four; withiromabout 0.001 to about ."10' weight percent, based on the .total weight 'oficyclic' ester, .of aluminum .trialkoxide; under substantiallyanhydrous conditions; for-a period of time suflicient tozproduce .a. polymer.

;2. A process which comprises polymerizing an ad- ;mixture comprising at least two cyclic esters which are -characterized. by the followingformula:

wherein each R, individually, is selected-from the group consisting of hydrogen, alkyl, aryl, alkaryl, ara1kyl,"cycloalkyl, halo, haloalkyl, alkoxyalkyl, alkoxy, -aryloxy, 'a portion of .an aromatic hydrocarbon nucleus which nucleus is fused to the cyclic ester-ring, and a portion of a saturated-'cycloaliphatic hydrocarbon nucleus which :nucleus contains from 4 to 10 carbon atoms and which is (a) the sum of 'x+y+-zcannot equal three, (-b) the total "number of atoms forming the cyclic ester ring does not exceed 18, and (c) the-total'number'of organic sub- "stituents attached to the carbon atoms contained in the cyclic ester ring does not exceed four; with from about 0.001 to about 10 weight percent, based on the total Weight of cyclic ester, of aluminum trialkoxide; under substantially anhydrous conditions; for a period of time sufficient to produce a polymer.

3. A process which comprises polymerizing deltavalerolactone with from about 0.01 to about 3.0 weight percent aluminum trialkoxide, based on the weight of said delta-valerolactone; at a temperature in the ran e of from about 0 C. to about 225 C.; under substantially anhydrous conditions; and for a period of time sufficient to produce a polymer.

4. A process which comprises polymerizing an alkylsubstituted delta-valerolactone with from about 0.01 to about 3.0 weight percent aluminum trialkoxide, based on the weight of said alkyl-substituted delta-valerolactone; at a temperature in the range of from about 0 C. to about 225 C.; under substantially anhydrous conditions; and for a period of time suflicient to produce a polymer.

5. A process which comprises polymerizing epsiloncaprolactone with from about 0.01 to about 3.0 Weight percent aluminum trialkoxide, based on the weight of said epsilon-caprolactone; at a temperature in the range of from about 0 C. to about 225 C.; under substantially anhydrous conditions; and for a period of time sufiicient to produce a polymer.

6. A process which comprises polymerizing an alkylsubstituted epsilon-caprolactone with from about 0.01 to about 3.0 weight percent aluminum trialkoxide, based on the Weight of said alkyl-substituted epsilon-caprolactone; at a temperature in the range of from about 0 C. to about 225 C.; under substantially anhydrous conditions; and for a period polymer.

is of timekufliciehtto produce a 7. A process which comprises polymerizing a monomeric lactone admixture comprising delta-valerolactone and an alkyl-substituted delta-valerolactone with from about 0.0l to about 3.0 weight percent aluminum trialkoxide, based on the total weight of the monomeric lactone feed; at a temperature in the range of from about -0 C. to about 225 'C.; under substantially anhydrous conditions; and for a period of time suflicient to produce a polymer.

8. A process which comprises polymerizing a monomeric lactone admixture comprising delta-valerolactone and epsilon-caprolactone with from about 0.01 to about 3.0 weight percent aluminum trialkoxide, based on the total weight of the monomeric lactone feed; at a temperature in the range of from about 0 C. to about 225 C.; under substantially anhydrous conditions; and for a period of time suflicient to produce a polymer.

9. A process which comprises polymerizing a monomeric lactone admixture comprising delta-valerolactone and an alkyl-substituted epsilon-caprolactone with from about 0.01 to about 3.0 weight percent aluminum trialkoxide, based on the total weight of the monomeric lactone feed; at-a temperature in the range of from about .0 C. to about 225 C.; under substantially anhydrous conditions; and for a period of time sufiicient to produce a polymer.

10. A process which comprises polymerizing a monomeric lactone admixture comprising epsilon-caprolactone and an alkyl-substituted delta-valerolactone with from about 0.01 to about 3.0 weight percent aluminum trialkoxide, based on the total weight of the monomeric lactone feed; at a temperature in the range of from about 0 C. to about 225 C.; under substantially anhydrous conditions; and for a period of time sufiicient to produce a polymer. V

11. A process which comprises polymerizing a monomeric lactone admixture comprising epsilon-caprolactone and an alkyl-substituted epsilon-caprolactone with from about 0.01 to about 3.0 weight percent aluminum trialkoxide, based on the total weight of the monomeric 1e lactone feed; at a temperatureiri the range of from about 0 C. to about. 225 C.'; under substantially. anhydrous Lconditions; and for a period of time sufficient to produce -a polymer; e

meric lactone admixture comprising an alkyl-substituted epsilon-caprolactone and an alkyl-substituted delta-valero- .lactone with from about 0.01 to about 3.0 weight percent aluminum trialkox'ide, based'on the total weight of 12. A process which comprises polymerizing a monothe monomeric latcone feed; at a temperature in the range of from about 0 C. to about 225 C.; under substantially anhydrous conditions; and for a period of time suflicient 10 produce a polymer.

13. A process which comprises polymerizing a monomeric lactone admixture comprising two alkyl-substituted delta-valerolacton'es with from about 0.01 to about 3.0

.weight percent aluminum trialkoxide, based on the total lweight of the monomeric lactone feed; at a temperature in the range of from about 0 C. to about 225 C.; under substantiallyanhydrous conditions; and fora period of time suificient' to produce a polymer.

14. A process'which comprises polymerizing a monomeric lactone admixture comprising two alkyl-substituted -epsilon-caprolactones'with from about 0.01 to about 3.0 weight percent aluminum trialkoxide, based on the total weight of the monomeric lactone feed; at a temperature in the range of from about 0 C. to about 225 C.; under substantially anhydrous conditions; and'for a period of ,time suflicient to produce a polymer. 

1. A PROCESS WHICH COMPRISES POLYMERIZING A CYCLIC ESTER CHARACTERIZED BY THE FOLLOWING FORMULA: 